The present invention, in some embodiments thereof, relates to a determinate castor, products thereof and methods of generating same.
Castor (Ricinus communis L.) is a non-food crop mainly utilized as a natural source of hydroxylated fatty acids. India, China and Brazil are traditionally the chief growers, while more developed countries are the major consumers of castor seed oil. In the 1960s castor was a promising crop in the Texas High Plains, but in 1972 changes in federal farm programs ended production in the USA. However, recently research efforts are resumed towards the production of castor seed oil containing significant levels of ricinoleic acid. This renewed interest in castor seed oil is also strengthened by the widespread applications of ricin as a potential therapeutic agent for many human diseases.
Castor is generally considered an annual crop herb, shrub or tree according to the different climatic zones, tropical or temperate, where it grows. In castor, the axillary buds into new shoots and branches. To allow the cultivation of castor in a modern agricultural context, the selection of a new genotype suitable for combine harvesting is desirable.
Castor genotypes with low tendencies to branch have been selected using the pedigree method, reviewed in Baldanzi and Pugliesi 1998 Plant Breeding 117:392-394. However successive rounds of self-pollination of these cultivars reduced plant vigor. It is reported that the selection for short and nonbranching castor plants usually has been difficult due to the high genotype vs. environment interaction (see Severino et al. 2012 Agronomy J. 104(4):853-880).
Flowering plants exhibit one of two types of inflorescence architecture: indeterminate, in which the inflorescence grows indefinitely, or determinate, in which a terminal flower is produced. Two important genes of the flowering pathways are FLOWERING LOCUS T (FT) and TERMINAL FLOWER 1 (TFL1). FT and TFL1 encode a pair of flowering regulators which function in diverse signaling pathways. FT and TFL1 share high level of homology (above 60% at the amino acid level) but function in an opposite manner. FT promotes the transition to reproductive development and flowering, whereas TFL1 represses it. Thus, a loss of function in TFL-1 has been associated with a determinate phenotype and early flowering.
To date transgenic silencing of TFL1 for obtaining a determinate phenotype and/or early flowering phenotype has been successfully implemented in various plant families (reviewed Dickland and Hanzawa 2015 Molecular Plant 1-15). However, in industrial plants from the Euphorbiaceae family, including prominent plants such as Jatropha, TFL-1 has recently been found to be a flowering promoter rather than a repressor. U.S. Patent Publication Number 20150033414 teaches a method of promoting flowering time in Jatropha and related plants e.g., castor, by transgenic expression of the flower promoting activity of the JcTFL1L-1 protein.